Farmland drainage automatic control circuit

During farmland drainage and irrigation, after the water in the rice fields or ponds is drained by the water pump, the water pump is still working. This not only wastes electricity, but also may
  burn the water pump motor . The farmland drainage and irrigation controller introduced in this example can promptly cut off the working power of the water pump
  motor , which can avoid damage to the permanent pump motor due to empty pumping without water. After adding this controller circuit, unattended drainage and irrigation can be realized, which is
  especially suitable for night operations.
    The farmland drainage and irrigation controller circuit consists of a power circuit, a water level detection control circuit and a control execution circuit, as shown in the figure.
    The power circuit consists of the step-down capacitor cI, the bleeder resistor R, the rectifier diodes VD1, VD2, the voltage stabilizing diode vs and the filter capacitor cz
.
    The water level detection control circuit is composed of water level detection electrodes a and b, resistors R2-R4, electronic switch integrated circuit and optical coupler VLC.
    The control execution circuit is composed of optocoupler VI-C, capacitor C3, resistor Rs, bidirectional trigger diode v. thyristor VTH and intermediate relay
KA.
  Knife switch Q, fuse FU, AC contactor KM, stop button Sl, start button S2 and thermal relay FR are the starting control and overload protection circuit of the water pump motor M.